Month: September 2022

MOLECULAR UNKNOWNS. "While the morphology and ultrastructure of silica deposition have been described in detail for a number of diatom species, little is known about the mechanisms of deposition at the molecular level. In an analogous way to coccolithophorid calcification." https://lnkd.in/eXTtntg View in LinkedIn

"BIOSILIFICATION in diatoms and sponges has been facilitated by small peptides – silafins and silicatein respectively at the molecular level. However, few other peptides such as frustulins and pleurolins have been identified to play a crucial role in the formation of biosilica. Silafins and silicateins isolated from diatoms cell wall and sponge spicules are demonstrated to induce in vitro formation of silica by hydrolyzing silicic acid or tetra ethoxy orthosilane." https://lnkd.in/es5DATt View in LinkedIn

ORGANIC NUCLEATORS. "The control by organisms on mineral expression is to a large extent attributed to the influence of organic molecules on nucleation and growth. Organic matrix frameworks can provide binding sites for the components of a mineral, selectively nucleating specific crystallographic faces, and organic carrier molecules can ensure supersaturation of a phase within mineralizing compartments. On a larger scale, shape regulation of such compartments can direct the morphology of biominerals forming within them." https://lnkd.in/eUUB9pU View in LinkedIn

NUCLEATION. "The first stage of biomineralization is nucleation of a ring of calcite nuclei with alternating orientations. This is a distinctive feature of heterococcoliths with no obvious parallels in any other biomineralization systems and has demonstrably remained constant through more than 200 million years of coccolith evolution...heterococcolith rim nucleation is characterized by a suite of features: alternation of c-axis orientations, control of a-axis orientations, stability through evolutionary history and chirality." https://lnkd.in/eUUB9pU View in LinkedIn

NUCLEATION. "The first stage of biomineralization is nucleation of a ring of calcite nuclei with alternating orientations. This is a distinctive feature of heterococcoliths with no obvious parallels in any other biomineralization systems and has demonstrably remained constant through more than 200 million years of coccolith evolution...heterococcolith rim nucleation is characterized by a suite of features: alternation of c-axis orientations, control of a-axis orientations, stability through evolutionary history and chirality." https://lnkd.in/eUUB9pU View in LinkedIn

ORGANIC TEMPLATES. "There is a substantial body of evidence to suggest that proteins and other organic molecules serve as “templates,” providing preferential sites for nucleation and controlling the orientation of the resulting crystals. Many organic-inorganic composites, including the shells of birds’ eggs and mollusks, exhibit a layered structure in which the inorganic component grows at the organic-solution interface." https://lnkd.in/eVX4ANS View in LinkedIn

NUCLEATION. "The presence of a foreign surface can be used to exert even greater control over nucleation because, quite often, the interfacial energy between a crystal nucleus and a solid substrate is lower than that of the crystal in contact with the solution. This is because the molecules in the crystal can form bonds with those in the substrate that are stronger than the bonds of solvation. Because the enthalpic contribution to the free energy comes primarily from chemical bonding, stronger bonds lead to a smaller interfacial free energy." https://lnkd.in/eVX4ANS View in LinkedIn

"CHIRALITY is a predictable result of nucleation on a biochemical substrate since virtually all organic macromolecules are chiral and occur in natural systems as only one enantiomorph. Therefore, a plausible model for the precise nucleation control around the margin of the organic baseplate is that a belt of macromolecular substrate occurs in this position with arrays of potential binding sites for calcium or carbonate ions which promotes nucleation of oriented calcite crystallites." https://lnkd.in/eUUB9pU View in LinkedIn

SOLUBLE SILICON. "While silica deposition and cell division can occur close to maximal rates at silicon concentrations that are limiting for silicon uptake, diatoms can accumulate soluble silicon between 20 and 400 mmol L(-1), exceeding the solubility for silicon and in some cases enough to synthesize an entire frustule without further silicon input." https://lnkd.in/eXTtntg View in LinkedIn

SATURATION. "There is evidence that calcification can frequently still occur when the external Ca2+ and/or CO3(2-) are so low as to cause undersaturation of the medium with respect to calcite...in the case of celestite and silica, the present surface ocean is well below the saturation value for these 2 minerals, and for silica this has been the case since (at least) soon after the appearance of diatoms in the fossil record...By contrast, the present surface ocean is supersaturated with respect to calcite, although this is forecast to change due to increases in CO2." https://lnkd.in/e2i9eMi View in LinkedIn